This invention relates to a machining centre for machining a workpiece, properly exchanging tools, and more specifically, to a machining centre with so-called armless-typed automatic tool changer.
A machining centre has a table for locating a workpiece thereon, a spindle for machining a workpiece by driving a supported tool, and an automatic tool changer for automatically exchanging a tool of the spindle, and is designed to machine a workpiece, properly exchanging tools. This automatic tool changer is an automatic tool exchanger with arm, which is comprised of an ATC arm, a shifter, an ATC arm driving unit, or an armless-typed automatic tool changer for exchanging tools by only operations of moving and positioning a tool magazine and a spindle without an ATC arm.
The latter armless-typed has a structure more simple than the former one with arm since an ATC arm, a shifter and an ATC arm driving unit are not necessary, thereby decreasing the cost of the unit and failure occurrence in tool exchange (see Japanese patent application; publication No. H06-218645).
Tool exchange operations in this arm-less type automatic tool changer are mentioned, referring to FIGS. 8 through 10. These figures are typically shown in order to show a conventional tool exchange method. That is, FIG. 8 is a typical explanation view showing ways of detaching the tool of the spindle and storing it in the tool magazine, FIG. 9 is a typical view showing ways of moving the tool magazine, and FIG. 10 is a typical view showing ways of installing the tool in the spindle.
In the figures, a reference number 111 denotes a spindle for driving a tool in order to execute machining operations on a workpiece, a reference number 121 denotes a tool magazine for storing various kinds of tools, a reference number Ai is a tool to be detached from the spindle 111 and to be stored in the tool magazine 121 (“the present tool” hereinafter), and a reference number Ai+1 denotes a tool to be scheduled to be installed in the spindle 111 (“the next tool” hereinafter).
FIG. 8(a) shows the way of moving the spindle 111 and inserting the present tool Ai in an empty pocket of the tool magazine 121. The present tool Ai is inserted into the empty pocket and, the engagement between the tool Ai and the spindle 111 is simultaneously released (see FIG. 8(b)). Thereafter, the spindle 111 is upwardly moved while holding the tool Ai by the pocket (see reference number U of FIG. 8(b) through (e)), and is stopped when the clearance between the spindle 111 and the tool Ai occurs (see FIG. 8(f)).
Next, the tool magazine 121 is rotated in the B direction for making the axial center CT1 of the spindle 111 close to the axial center CT3 of the next tool Ai+1 (see FIG. 9(a) through (f)), and the rotation of the tool magazine 121 is stopped when corresponding both the axial centers CT1 and CT3 with each other (see FIG. 10(a)). The spindle is lowered at the rotational position, and the next tool Ai+1 is installed (see number D of FIG. 10(b) through (f)).
Thereafter, the spindle 111 and the tool Ai+1 are separated from the tool magazine 121, and the machining operation on the workpiece is restarted.
In case of the above-mentioned armless typed automatic tool changer, the movement U and the stop of the spindle 111 (see FIG. 8), the movement B and stop of the tool magazine 121 (see FIG. 9) and the movement D of the spindle 111 (see FIG. 10) are executed in this order, so that the tool exchange takes a longer time and the producibility is not so good.
Under these situations, a machining centre for decreasing the machine cost and the error occurrence at the time of tool exchange, and for actualizing speedy tool exchange has been desired.